1. Field of the Invention
The present invention generally relates to the field of door openers and, more particularly, to a drive device for a hatch of a motor vehicle.
2. Description of the Related Art
Conventional drive devices for the hatch of a motor vehicle typically include a first fastening element that can be connected to a stationary component or to a movable component and a housing tube that is located at an end of the drive device opposite to the first fastening element. The housing tube is able to move axially relative to the first fastening element and has a second fastening element on the end opposite the first fastening element, where it is possible to connect this second element to the movable component or to the stationary component.
The drive device also includes a spindle drive that comprises a threaded spindle and a spindle nut that is mounted on the threaded spindle. The spindle drive permits the first fastening element and the housing tube to be driven axially relative to each other. In addition, the spindle drive can be rotatably driven by an electric motor, where the output shaft of the motor can rotate the threaded spindle or a connecting component of a clutch.
In such conventional drive devices, it is known that the electric motor can be produced as a completely independent unit having its own motor housing, which is then installed in the housing tube. However, this requires not only a large number of components but also a great deal of care in the installation of the electric motor to ensure that it is coaxial to the threaded spindle or to the clutch provided in the housing tube.
In drive devices of this type, the electric motor must be designed such that it can reliably move a component to be moved under any normal operating conditions. In the case of movable components which are relatively heavy, a correspondingly powerful electric motor must be used, the size of which will also be considerable, especially with respect to its diameter. This leads to a drive device which requires a large amount of installation space.
It is therefore apparent there is need for a drive device of the above-indicated type which is small in size and which especially has a small diameter.